Modulation system



Oct. 24, 1933. c cum 1,932,155

MODULATION SYSTEM Filed Ogt. 14, 1931 INVENTOR Charles A. lIulvBI' ATTORNEY Patented Oct. 24, 1933 v i 1 932 155.

chirp srA-rss ATENT o r-r ce MODULATION SYSTEM, Charles A. Culver, Northfield, Minn. Application October 14, 1931. Serial'No. 568,663

A 1 Claim. (01. 179-471) My invention pertains ingeneralto radio sig to an inductancev 12. A condenser 13" 'is'connaling and specifically relates to a system for nected in parallel with the inductance 10. A modulating high frequency energy. source of anode'voltage 14 is provided in circuit One of the objects ofmy invention consists with the anode and cathode of space discharge in providing a simple and efiicient system for tube 8,as shown. Thev inductance 12 is connected 60 modulating sustained high frequency oscillations. with a load 16 which is indicative of any work Another object consists in producing a moducircuit for the utilization ofmodulated high frelation system in which the resistance of space quency oscillations, such as an antenna system.

discharge tube controls the output of a high fre- In accordance with the system of my invention, quency circuit in accordance with modulation a space discharge tube 18 is provided having 65 energy. the anode and cathode thereof connected across I accomplish these and other desirable ohthe inductance 6 whereby the space discharge J'ects in a novel modulation system employing a tube 18 serves as a resistance in shunt with the microphone controlled space discharge tube for inductance 6. A microphone 19 is connected in producing a variable resistance to effect the mod-- series with a source of voltage 26 and inductance 70 ulation of high frequency oscillations. 21, which circuit is indicative of any source of In the drawing which accompanies and forms modulation energy. The inductance 21 forms a part of this specification and in which like the prim ry Of an audio frequency transformer reference numerals designate corresponding parts having the secondary Winding thereof connected throughout: between the grid and cathode of space discharge 75 Fig. 1 is a diagrammatic representation of one tube 18. A source of biasing voltage 22 is conembodiment of the modulation system of my innected in series with the winding 23 as shown. ventio and In the operation of my system for producing Fig. 2 is a diagrammatic representati of an modulated high frequency oscillations, the source 25' alternative form of the circuit arrangements of 1 p c high fr q n y O c ations Which are the system of Fig. 1. amplified by the amplifier tube 2. These high My invention contemplates providing a mod frequency oscillations traverse the inductance 6 lation system in which modulation energy imand are directed throu o denser '7 to the pressed between the cathode and anode of a space grid o Space discharge tube e C cui 19--v 30 discharge tube varies the internal resistance of 20-21 induces voltages in the winding 23 which the space discharge tube for controlling a high C nt l e internal, 0 a ode to cathode refrequency circuit. In accordance with my insistence the Space discharge tube 18 in vention, a space discharge tubev is employed as a accordance with the modulation energy under variable resistance to control the amplitude of control of the microphone 19. This variation 35 high frequency oscillations fed into a high freof the resistance of space discharge tube 18 acts quency amplifier tube. as a variable resistance in shunt with inductance Referring to the drawing in detail, and specifi- 6 for controlling h mp ud f t e high frecally to Fig. 1, there is provided a source of high quency Oscillations pressed upon space disfrequency oscillations 1 connected between the Charge tube The amplified high que cy 40 grid and cathode cf 3, p'acgdischarge amplifier 08011131310115 available t0 the load 16 Will therefore 2 tube 2 having a source of biasing voltage 3. Th be modulated in accordance with modulation output or anode to cathode circuit of the space energy under Control microphone discharge tube 2 includes an inductance 6 and Fig. 2 is an alternative a e ent of the a source of anode voltage 4. The condenser 5 is Circuit of Referring to t e in- 45 connected in parallel with the inductance 6. ductance 5 is r -maenetically coup to A connection is provided from inductance 6 alhindlllctance 15 connected between the d through the condenser '7 to the grid of a space aml cathode of Space c arge tube 8. The discharge amplifier tube 8. A connection is also Output t0 cathofie Circuit of the Space provided from the cathode of space discharge discharge llllbe 18 then includes inductance 15 50 tube 8 to the inductance 6. A source of biasing by e space discharge tube 18 .serves as a voltage 9 is connected, as shown, between the variable resistance in shunt with the inductance cathode and grid of the space discharge tube 8.- 5, as be o e. O e Ci cu t Components shown The output or anode to cathode circuit of space in Fig. 2, as well as their operation, are substandischarge tube 8 includes a condenser 11 and tially similar to Fig. 1. Although Fig. 2 shows an i d tance 10 electro-m'agnetically coupled an alternative of the circuit arrangement of Fig. 1, it will, of course, be understood that various other modifications can be made Without departing from the intended scope of my invention. For example, the anode and cathode connections of space discharge tube 18 with reference to the space discharge tube 8 might be reversed.

It will now be evident that I have provided a novel form of modulation system which I have found in experiments produces faithful modulation and which offers many advantages in its use. One of the chief advantages accruing from my system resides in that the use of a modulation choke, or the use of any iron or other magnetic material is avoided, whereby the fidelity of modulation is greatly improved. Although I have shown a preferred embodiment of my modulation system I do not desire to be limited thereto except insofar as may be pointed out in the appended claim.

What I claim as new. and original and desire to secure by Letters Patent of the United States A modulation system comprising, a source of high frequency oscillations, a space discharge amplifier including a cathode, and anode, and a grid, said grid and cathode being connected to said source of high frequency oscillations, an inductance, said cathode and anode being connected to said inductance, a second space discharge amplifier, input and output circuits therefor, the input circuit of said second space discharge amplifier being connected to said inductance, a load, the output circuit of said second amplifier being connected to said load, a third amplifier including a cathode, an anode and a grid, the anode and cathode of said third amplifier being connected in series with said inductance and a circuit connected between the grid and cathode of said third amplifier for causing modulation energy to control the internal resistance of said third amplifier to vary the amplitude of said high frequency oscillations directed to said second amplifier.

CHARLES A. CULVER. 

